What is the fertile window?

The fertile window is the 6 days leading up to and including ovulation. The 2 days before ovulation are the most likely time to conceive.

How does cycle length affect ovulation?

Ovulation happens roughly 14 days before your next period. If your cycle is 28 days, ovulation is around day 14. If your cycle is 32 days, ovulation is around day 18.

Is this calculator accurate?

It gives an estimate based on average cycles. Tracking basal body temperature, cervical mucus, or using an ovulation predictor kit gives a more precise signal.

What if my cycles are irregular?

Irregular cycles make the calendar method less reliable. If your cycles vary by more than 7 days, consider tracking ovulation signs directly or consulting your provider.

Ovulation calculator

Find your fertile window and likely conception dates based on your last period and cycle length.

First day of your last period

Average cycle length (days)

Common questions

The fertile window is the 6 days leading up to and including ovulation. The 2 days before ovulation are the most likely time to conceive.
Ovulation happens roughly 14 days before your next period. If your cycle is 28 days, ovulation is around day 14. If your cycle is 32 days, ovulation is around day 18.
It gives an estimate based on average cycles. Tracking basal body temperature, cervical mucus, or using an ovulation predictor kit gives a more precise signal.
Irregular cycles make the calendar method less reliable. If your cycles vary by more than 7 days, consider tracking ovulation signs directly or consulting your provider.